Exercise is all that matters when it comes to losing weight fast.

The bulk of research shows us that, in the short term, diet is far more important than simply upping your workout regimen if you want to start shedding pounds.

"Studies tend to show that in terms of weight loss, diet plays a much bigger role than exercise," Philip Stanforth, an exercise scientist at the University of Texas and the executive director of the Fitness Institute of Texas, told Business Insider.

Research suggests that regular workouts become more important for staying fit over the long term, though.

"When you look at people who've lost weight and are also managing to keep it off, exercise is important," Stanforth said.

Early morning is the only time you should work out.

Afternoons or evenings are likely nearly as good for you as early-morning workouts, according to several studies.

But some research suggests that working out first thing each day helps speed weight loss and boost energy levels by priming the body for an all-day fat burn.

Plus, getting more daylight may play an important role in shedding pounds. By aligning our internal clocks — or circadian rhythms — with the natural world, we may help give our metabolisms a boost. One study showed that people who basked in bright sunlight within two hours after waking tended to be thinner and better able to manage their weight than people who didn't get any natural light, regardless of what they ate throughout the day.

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Women shouldn't weight train because they'll bulk up like a man.

In a recent poll by the fitness equipment company Nautilus, only 13% of respondents said they thought women could weight train without "bulking up like a man."

Guess what? It is perfectly safe for everyone to lift weights — and it's also a great way to strengthen your muscles. The ability to build large muscles is directly dependent on the amount of testosterone we have, and women produce far less testosterone on average than men. So if you're a woman, the chances that you'll "bulk up" are incredibly slim — pun intended.

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A few minutes on the treadmill will jump-start your fat burn.

You have to burn 3,500 calories— far more than the equivalent of the total number of calories an average adult should eat in an entire day— to burn or lose a pound of fat. For some perspective, the average American adult man would burn roughly 330 calories from running at a moderate pace (i.e., a nine-minute mile) for 20 minutes.

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Keeping a food diary is a reliable way of monitoring what you eat.

Even when we're making an effort to be more conscious about what we're putting into our bodies and how active we're being, we tend to give ourselves more credit than we deserve.

"People tend to overestimate their physical activity and underestimate how much food they eat," Stanforth said. "They consistently think they've worked out more and consistently think they've eaten less."

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You have to cut carbs or sugar to lose weight.

The problem with fad diets is simple: They're temporary. In order to lose weight and keep it off, you have to find an eating regimen that you can stick with for life.

"You know we tend to say you go on a diet, but that also implies you're going to go off of it. And that's not how we should be looking at this," Stanforth told us. "Sometimes people are looking for the latest fad, but oftentimes it's the fundamentals that are the most important and that make the biggest difference."

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Running a marathon is the best way to get fit.

Good news: You can stop feeling guilty about not signing up for that marathon everyone's talking about. As it turns out, you can get some of the same benefits of long-distance running without ever passing the 5-mile mark.

Running fast and hard for just five to 10 minutes a day can provide some of the same health benefits as running for hours can. In fact, people who run for less than an hour a week — so long as they get in those few minutes each day — get similar benefits in terms of heart health compared with those who run more than three hours a week.

Working out for one or two days a week is enough to stay in shape.

If you're already in decent shape, exercising for a couple of days a week likely won't benefit you much.

"A minimum of three days per week for a structured exercise program" is best, Shawn Arent, an exercise scientist at Rutgers University, told Business Insider. "Technically, you should do something every day, and by something I mean physical activity — just move. Because we're finding more and more that the act of sitting counteracts any of the activity you do."

Sports drinks are the best thing to have on hand after a workout.

Sorry, Gatorade lovers. This "power beverage" is mostly just sugar and water.

Experts recommended refueling the body after a workout with about 20 grams of protein— from any source — and lots of water.

"Protein ingestion during and/or immediately after exercise has been suggested to facilitate the ... adaptive response to each exercise session, resulting in more effective muscle reconditioning," according to a paper from the Nestle Nutrition Institute Workshop Series.

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It takes at least a couple of weeks to get out of shape once you stop working out.

Flickr/MarionDoss

Sadly, all those brawny muscles you worked so hard to build this summer will likely start to break down a few days after you cut back in the fall.

In most people, muscle tissue can start to break down within a week without regular exercise.

"If you stop training, you actually do get noticeable deconditioning, or the beginnings of deconditioning, with as little as seven days of complete rest," Arent said. "It very much is an issue of use it or lose it."